Tuning water chemistry for the recovery of greener products: pragmatic and sustainable approaches

Abstract

The early techniques for recovery of bioactive metabolites involve conventional cold or hot solvent extraction.1 The choice is a function of the nature of the bioactive compound of interest.2 The adverse effect of organic solvents (Table 1) which are mostly preferred extraction techniques has warranted the search for greener alternatives. One of the ways green extrac tions is described involves the isolation of medicinally active portions from a bio-material,3 with the simultaneous use of eco friendly solvents and optimal use of energy.4–9 Prospecting for green solvents has brought water to the fore of extraction technology.10 Water is affirmatively described as the “greenest solvent” imaginable, with its availability at the required purity, it is cost-effective, readily recycled, non-toxic, non-ammable, and eco-friendly.10–13 Based on the green chemistry precept, water is considered a green chemical per excellence.14–16 Water is useful in the recovery of various phytochemicals including alcohols, sugars, proteins, and organic acids with natural water soluble properties.12,16–21 However, water as a solvent has some physical and chemical property disadvantages when compared to organic solvent.21–23 The polar nature of water in its natural form reduces its efficacy and acceptability when compared with organic solvents for some kinds of extractions. Organic solvents are extensively desirable since they exhibit better recovery than water at ambient conditions.3 Further setbacks experienced when using conventional hydro-extraction include time and energy consumption, thermal decomposition of thermo sensitive metabolites and low recovery of hydro-solvent in its natural form. There exists the need to investigate water properties that can be improved to complement its natural advantage and eradicate its attendant limitations as a solvent for extraction.5,8,10,28,29 have indicated that improving traditional extraction must entail decreased energy input, sustainability and a non-toxic nal product. Improving water to own variable chemistry will aid the extraction of a broad range of polar and non-polar biomolecules from sustainable natural products with non-toxic quality and eco-friendliness.10,21,29 This approach will prevent the use of organic solvents, fossil energy, chemical waste and risks of extraction. It is known that water existing in its tunable form satises the conditions of green solvents.11–13 Recently, the